1. Field of the Invention
The present invention relates to an oscillator for the microwave band or the milliwave band provided with an oscillation circuit using a Gunn diode, etc., and an output transmission line to output an oscillation signal. The invention further relates to radio equipment using the oscillator.
2. Description of the Related Art
Up to now, oscillators for the microwave band and the milliwave band using a negative-resistance element such as a Gunn diode, etc., have used a dielectric resonator as an output transmission line, as shown in (1) Japanese Unexamined Patent Application Publication No. 6-268445 and (2) Japanese Unexamined Patent Application Publication No. 9-205324.
In this way, when the dielectric line is utilized as an output transmission line, an oscillator of high performance can be constructed by making the best use of the resonator""s low loss characteristics.
However, in the conventional oscillator shown in the above-mentioned Japanese Unexamined Patent Application Publication No. 6-268445, because a stripline and a dielectric line are coupled by a three-dimensional arrangement, the degree of coupling and other factors are varied by the length of the stripline and the location of its open ends. Therefore, it is difficult to achieve coupling between the dielectric line (hereinafter, called an xe2x80x9cNRD guidexe2x80x9d) and the dielectric resonator at locations to obtain the most appropriate phase relationship. Moreover, in the coupling portion between the stripline and the NRD guide, another problem is that because the symmetry to the left and the right collapses, unwanted modes of electromagnetic field are easily generated.
Furthermore, in the conventional oscillators shown in both Japanese Unexamined Patent Application Publication No. 6-268445 and Japanese Unexamined Patent Application Publication No. 9-205324, it is necessary to dispose the dielectric resonator in a space between upper and lower conductor plates, that is, a cutoff area of an NRD guide, and accordingly it is difficult with these devices to obtain an oscillator of smaller size.
Accordingly, the present invention provides an oscillator in which the above-mentioned problems are solved. With this oscillator, it is easy to design and adjust the coupling portion between a stripline and an NRD guide, unwanted modes are suppressed, and the size is reduced. The invention also provides radio equipment using the oscillator.
In an embodiment of an oscillator of the present invention which is provided with an oscillation circuit constructed on a dielectric substrate and an output transmission line which transmits an oscillation output signal from the oscillation circuit, a line made up of a conductor pattern is constructed on the dielectric substrate, a negative-resistance element is connected to the line, a dielectric resonator is disposed in the vicinity of the line on the dielectric substrate, this dielectric resonator is coupled to the line, and between the connecting location of the negative-resistance element and the coupling location of the dielectric resonator in the line, the line is coupled to the output transmission line.
In another aspect of an oscillator of the present invention, the output transmission line is made up of a dielectric line in which a dielectric stripline is disposed between two nearly parallel conductor plates.
In another aspect of an oscillator of the present invention, when the wavelength on the line is denoted by xcexg, the length from the connecting location of the negative-resistance element to an end portion in the vicinity of the line is made xcexg/4+N1xc3x97xcexg/2 (wherein N1 is an integer greater than zero), the length from the connecting location of the negative-resistance element to the coupling location of the output transmission line is made N2xc3x97xcexg/2 (wherein N2 is an integer greater than zero), and the length from the coupling location of the output transmission line to the coupling location of the dielectric resonator is made N3xc3x97xcexg/2 (wherein N3 is an integer greater than zero).
In another aspect of an oscillator of the present invention, the dielectric resonator is constructed by providing electrodes having an opening portion on another dielectric substrate with which the dielectric substrate is laminated.
In another aspect of an oscillator of the present invention, a secondary line to be coupled to the dielectric resonator is provided on the dielectric substrate, a variable reactance element is connected to the secondary line, and a line is provided for supplying control voltage to the variable reactance element.
In another aspect of an oscillator of the present invention, the output transmission line is made up of a transmission line in which a portion of dielectric material is contained between two nearly parallel conductor surfaces and which has cutoff characteristics, and the cutoff frequency of the transmission line is determined so as to cut off the fundamental wave component, or the fundamental wave component and lower-order harmonics, and so that the harmonic components of higher order than the cut-off components are transmitted.
In another aspect of an oscillator of the present invention, a terminal which is weakly coupled to the oscillation circuit is provided.
In another aspect of an oscillator of the present invention, the output line is made up of a dielectric line in which a dielectric stripline is disposed between nearly parallel conductor plates, and by forming a slot in one conductor plate and by disposing the dielectric substrate outside the conductor plate, a line of the oscillation circuit and the dielectric line are coupled.
In another aspect of an oscillator of the present invention, the dielectric substrate is housed inside a case, a portion of wide line width and a portion of narrow line width are provided in the bias line, and in the vicinity of a portion of narrow line width a spring for fixing the dielectric plate on the inside surface of the case is provided.
Radio equipment embodying the present invention can be constructed by using any one of the above oscillators.
Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings, in which like references denote like elements and parts.